Microplastic and microfibre pollution in confined aquifers: insights from Italy

Groundwaters are essential resources for environment and societies, especially for its use in agriculture and as drinking water. Growing evidence suggests that microplastics (MPs) accumulate in soil and infiltrate in groundwaters, ranging from 0.1 to thousands items/L. However, groundwaters researc regarding MPs are lacking, especially in confined aquifers, and microfibre (MF) studies are at the early stages. Aquifer waters are often used for human consumption, however, even confined aquifers are not immune to seepage, especially where geology is complex or human activity modified natural stratigraphy. These aquifers are particularly vulnerable to pollution, as their limited exchange and slow flow rates can favor long-term accumulation. This study investigated anthropogenic microparticles (AMPs), such as MPs and MFs, in 25 confined aquifers of the NW Italy. AMPs were found in all sampling points, (mean and SD of 90.0 ± 64.3 AMPss/L) however, only 2.1% were synthetic. MPs were found in 13 aquifers, ranging from 0 to 6.3 MPs/L (mean and SD of 1.9 ± 2 MPss/L). Vinyl compounds and copolymers were the main types of MPs found, followed by polyesters, and other synthetics. Fibres represented major part of the AMPs (95.2%) followed by fragments (4.6%), however, MP were especially fragments (72.0%). Big particles (5-1 mm) accounted for only 17.3%, highlighting the increase of micropollutants with the decrease in the size considered. Possible sources of pollution could be linked to nearby human activities, especially agricultural ones, and water intakes, providing useful references for further research. Given the susceptibility of groundwater resources to contamination, anthropogenic stressors, and climate variability, alongside their essential ecological functions and significance as a primary source of potable water, it is imperative to implement strategies focused on subsurface environment protection and sustainable management of water resources. Consequently, MP and MF investigations are required to elucidate groundwater system dynamics, evaluate environmental health conditions, and identify potential sources.